First, Elon Musk has already been dismissive of COVID-19 safeguards and outright ignored previous shutdown orders calling them fascist and threatened to leave California because of them. He has frequently tweeted multiple debunked claims and theories.

He said in his latest tweet that something extremely bogus is going on with testing, but the FDA has already admitted to the challenges with the rapid antigen tests. Therefore nothing bogus was happening, just issues that were already publicly known, however Musk has made it clear that he is against precautions so it benefits him to spread confusion and doubts about the virus and testing because he doesn't want to lose any profits from the impact caused by shutdowns.

It sounds like you're mostly taking issue with his other views around covid. Fair enough, but I don't think he was entirely wrong to call a test that seems nearly random bogus.